Electric circuit breakers are common and are generally used in pairs or groups with a handle. The position of the handle typically indicates the status or condition of the breaker. The handle usually has three different positions one at each extreme throw of the handle and an intermediate position between the two extremes. One extreme indicates the breaker is switched on, the other extreme indicates the breaker is switched off and the intermediate position shows when the breaker is "blown". "Blown" is a condition where a short circuit, or near short circuit, occurred and the current flowing through the breaker exceeded the rating of the breaker causing the breaker is open, and so disconnect the power source from the load.
U.S. Pat. No. 4,004,201 issued to Robert DePuy discloses a multi-function solid state trip unit for automatic electric circuit breaker incorporation indicator functions. These indicator functions signal when a short circuit, overload or ground fault occurred. This patent is a complex arrangement where sensitive detection circuits are used to detect the load conditions of the breaker. When a short, overload or ground fault occurs the detection circuits respond and through programmable timing circuits drive SCR's which trip the breaker. These SCR's also are connected to indicators which signal which condition occurred. The patent also discloses a bypass circuit which insures that tripping of the breaker is not jeopardized by failure of the indicators.
A limitation of the DePuy patent is its reliance on complex detection and driving circuits requiring a separate power supply. This extra, complex circuitry adds cost and other reliability considerations. Also the DePuy circuitry is magnetically coupled to the breakers, it is not physically connected to the breaker circuitry so that the actual condition of the lines connected to the breaker may not be shown by the indicators.
U.S. Pat. No. 4,056,816 issued to Raul Guim discloses a "light emitting diode (LED) blown circuit breaker indicator." Here the LED is connected in parallel across the circuit breaker terminals by a separate set of contacts. These contacts are arranged similarly to a single pole double throw switch. These separate contacts are arranged such that when the breaker is not blown these separate contacts are opened and the LED circuit is not powered. When the breaker is blown the main breaker contacts are opened disconnecting the load from the power source. But, in this invention, the separate set of contacts are now made and the LED circuit is connected from the power source to the load. Since the load presumably is a short (since the current was enough to blow the breaker) the LED circuit is completed through the load and the LED is turned on. In this way the LED shows the blown breaker which is an object of the invention. U.S. Pat. No. 4,760,384 issued to Oscar Vila-Mascot shows an improvement on the Guim patent. The improvement is to replace the LED with an active component, a capacitor is shown, so that the power requirements are more controlled than in Guim's circuit. There are other claimed benefit and an alternate arrangement where the light is on when the breaker is not blown and off when the breaker is blown. Both of these patents use a separate set of contacts to complete the circuit for the indicator lights, which adds complexity to the arrangement. Furthermore there is no indication that the load circuit is properly receiving the input power.
U.S. Pat. No. 3,742,402 issued to Ronald Nicol et al., discloses a circuit breaker with an on, off and trip indicator. However in this invention the state of the breaker is determined by differing paths traversed by the breaker arm when the breaker was switched off purposely as compared to an overload which .about.blows.about. the breaker. In this invention there are in fact two different switches with complex mechanical linkages which are costly and difficult to maintain.
There is a need for a simple, low cost, easy to maintain and manufacture circuit breaker which indicates the state of the breaker.
An object of this invention is to provide a means to indicate the state of a circuit breaker without a costly and complex mechanical design. It is an object of this invention to indicate the state of the breaker, on, switched off and blown or tripped.
It is another object of this invention to indicate the condition of the load circuit, e.g. a short still exists or not.